High surface area zirconia by digestion of zirconium propoxide at different pH

The microstructure of hydrous zirconia (ZrO2) prepared by the hydrolysis of zirconium propoxide followed by digestion at pH 1, 3 and 9 and the ZrO2 de rived from this precursor have been studied. The undigested hydrous oxides formed plate-like aggregates with low porosity. After digestion at pH 9, th e hydrous oxides became highly porous with surface areas up to 550 m(2)/g. Calcination at 500 degrees C for 12 h results in ZrO2 with surface areas of more than 380 m(2)/g, ZrO2 formed after digestion in acidic medium had low er surface areas of less than 100 m(2)/g and were mixed in tetragonal and m onoclinic phases. The water/propoxide ratio during gel formation influences the surface area of the resulting ZrO2. The thermal stability of the mater ial is remarkable: ZrO2 resulting from long digestion retained up to 100 m( 2)/g after successive heating to 900 degrees C. The observed microstructura l properties are attributed to the nature of the alkoxide precursor formed under different water/alkoxide ratios and to the effects of digestion under varying pH conditions. (C) 2000 Elsevier Science B.V. All rights reserved.